During the coming year we propose to continue development of rhesus monkey models of human depressive disorders, with special emphasis on production and evaluation of depression in adolescent and adult subjects. We will employ three different induction techniques: (a) learned helplessness paradigms, (b) prolonged sequences of repetitive peer separations, and (c) depletion of specific brain amines concomitant with social separations. For subjects in each induction condition, as well as for controls, we plan to collect social interactive behavioral data, measures of motivation and cognitive functioning, and (for a subsample of the subject population) samples of plasma and CSF for subsequent assay. These measures will be collected and analyzed in a manner designed to facilitate direct comparisons among the above induction techniques for efficacy of production of depression in our adolescent and adult subjects. In addition, it will be possible to compare these findings with data collected on depressed infant subjects, in order to assess the relationship between infantile and adult forms of depression in rhesus monkey subjects. BIBLIOGRAPHIC REFERENCES: Suomi, S. J. Factors affecting responses to social separation in rhesus monkeys. In G. Serban & A. Kling (Eds.), Animal models in human psychobiology. New York: Plenum Press, 1976. Pp. 61-74. Suomi, S. J., Collins, M. L., Harlow, H. F., & Ruppenthal, G. C. Effects of maternal and peer separations on young monkeys. Journal of Child Psychology and Psychiatry, 1976, 17, 101-112.